The present invention relates to a process for crystallizing amorphous lactose in dried whole milk powder and to the chocolate products prepared therefrom.
Dried whole milk powder is derived from whole milk and is used for a great variety of purposes. For example, whole milk powder is an ingredient in bakery products, such as dry baking mixes for the preparation of home-made cakes and the like. It is also used in the production of confectionary products, such as chocolate, e.g., milk chocolate, white chocolate, semi-sweet-chocolate, and the like.
The process of making milk chocolate requires several steps. In the first step, a nutritive carbohydrate sweetener, such as granulated sucrose is combined and mixed with cocoa butter, chocolate liquor and whole milk powder to form a paste. Next, in the refining step, essentially a fine grinding operation, the coarse paste from the mixer is passed between steel rollers and converted into a refined flake. The refining step breaks up the crystalline nutritive carbohydrate sweetener, cocoa butter, and milk solids such that the sizes of the particles are significantly reduced. This particle size reduction results in the desired smoothness of the chocolate. The third step is the conching step, which is a mixing-kneading step. In the conching step, the mixture is slurried while heating to give the final desired consistency of the milk chocolate. This mixing-kneading process allows moisture and volatile components to escape while smoothing the chocolate paste and is critical to the flavor and texture development of the chocolate. In the next step, i.e., the standardizing and finishing step, additional fat and emulsifier are added to the conched mixture to adjust the viscosity to the final specifications. The final step in obtaining the desired rheology of the chocolate is the tempering step, a process of inducing satisfactory crystal nucleation of the liquid fat in the chocolate.
Chocolate is a food substance which comprises chocolate liquor and cocoa butter, both derived from cocoa beans, and sugar. When milk chocolate is prepared, however, the formulation includes non-fat milk solids and milkfat as well. In order for the designation xe2x80x9cmilk chocolatexe2x80x9d to be applied, however, there must be no less than 12% of milk solids included in the milk chocolate formulation.
The milkfat and non-fat milk solids in milk chocolate are derived from dried whole milk powder. Thus, whole milk powder is an ingredient of milk chocolate.
Dried whole milk powder is made from fluid milk and contains lactose, milk proteins, milk fat and milk minerals in the same relative proportions to one another as the milk from which it was made. Thus, the fat system in the milk chocolate is the combination or blend of the cocoa butter together with the butter fat carried into the chocolate formulation by dry whole milk powder.
The most common commercial process for preparing the milk powder is xe2x80x9cspray dryingxe2x80x9d. The effect of spray drying is, in any event, to use heat to evaporate the water constituent of whole milk and to remove it as water vapor. This process is performed quickly and does not provide sufficient time for the lactose in the milk powder to crystallize; as a result, the lactose is amorphous. Moreover, and more importantly, as a result of this process, a considerable portionxe2x80x94usually no less than about 85% of the fat constituent found in whole milk powderxe2x80x94becomes encapsulated in the serum solids, i.e., the amorphous lactose forms a matrix with the milk protein that encapsulates fat globules.
Thus, a particular problem that faces the chocolate maker is that only a certain amount of fat is available from the dry whole milk powder, which has been manufactured using traditional methods for production thereof, for entry into the chocolate formulation as a fat constituent. It can only be made available by further mechanical processing steps, whereby the fat is effectively squeezed out of its encapsulation carriers and added to the formulation for use as fat. This can be accomplished by passing the blended cocoa butter and chocolate liquor, sugar, and dry whole milk between closely spaced rollers so as to refine or conch the product. Indeed only about 60% of the fat content of conventional dry whole milk powder is available for fat extraction after refining and entry into the chocolate formulation as fat. It is believed that 40% or so of the fat constituent which is encapsulated in the serum products of the dry whole milk can not easily be removed so as to become available as fat. What that means is that as the dry whole milk enters into the formulation of the food product, such as the milk chocolate, the unrecoverable fat is not available to enter the fat system of the food product and is thus unavailable as fat during further preparation steps, and cannot be used to facilitate the preparation thereof, as e.g., for lubrication.
If the product is not fully refined or conched, and milkfat is utilized in the food product formulation, especially when the food product is milk chocolate, then there may in fact be a higher amount of fat present in the food product than is useable. That unusable fat nonetheless enters the body of the person consuming the food product as fat nutrient. Still further, of course, that unavailable fat constituent does not enter into the fat system with cocoa butter, for example, as the milk chocolate is being prepared.
Moreover, in the amorphous state, lactose is hygroscopic. A small portion of water, sometimes up to 5%, may also be encapsulated or bound in the protein constituent of the milk and cannot be removed therefrom. Further, the moisture absorbing property of the powdery milk is so high, that if placed in water, the milk powder absorbs water to form a syrup layer. It has been found that when the moisture content of the powder approaches 7% or higher, the amorphous state of the lactose will change and crystallization of lactose will occur. However, when lactose in milk powder crystallizes in this manner, as a consequence of moisture absorption, problems with caking and lumping occur. More specifically, when placed in water, the contact portion of the powder with water is rapidly made wet and forms a highly viscous syrup layer, with the result that the capillary space leading into the inner region of the powdery means is plugged to prevent water from permeating into the powdery mass. It follows that the powdery milk forms lumps and is not dissolved in water. Moreover, the simultaneous occurrence of non-enzymatic browning occur when lactose is crystallized in this manner.
It follows, therefore, that the chocolate industry, in particular, recognizes the difficulties in formulating milk chocolate when not all of the fat from the dry whole milk powder constituent being used is available as fat.
One solution of this problem is described in WO 00/21380 in which the milk powder is processed at elevated temperatures with shear in a mixing or grinding device such as a 2xe2x80x3 or 5xe2x80x3 continuous process or manufactured by Readco Manufacturing Company in York, Pa., to form a milk powder containing crystallized lactose. However, the patent application notes on Page 8 thereof that xe2x80x9cThere was a noticeable rise in the power requirements of the processor as the lactose crystallized.xe2x80x9d The present inventors also observed that when crystallization of the lactose starts, the viscosity of the mass increases significantly and the power requirement literally increases dramatically, e.g., from 5 Hp to 40 Hp, within seconds. They further noted that the kinetics of the reaction is uncontrollable, and the products either burn or the processor overloads.
The present inventors thus searched for a process which would impart enough energy to crystallize the lactose in the milk powder, but required less energy input than the process described hereinabove, and which was not accompanied by the huge power surge as described hereinabove. The present inventors found such a process.
The present invention, however, avoids the difficulties described hereinabove including the power surge described hereinabove. The present inventors have found that proper crystallization of lactose in the milk powder can be obtained and the difficulty described in WO 00/21380 can be overcome if simultaneous with or prior to the heating and shearing, the milk powder is contacted with a sufficient amount of water.
The present inventors have found that their method is a fast and efficient means of converting the amorphous lactose in the dry milk powder to the crystalline form. Moreover, when the lactose is crystallized in accordance with the present process, the inherent problems of caking, lumping and browning associated with prior art milk powders is significantly mitigated and/or even eliminated.
So as to provide for the production of dry milk powder which has substantially all of the fat constituent recoverable as free fat when the dry milk powder is blended as dry whole milk powder into milk chocolate, dry baking mixes or other foods, the present invention provides a method for crystallizing the lactose in the milk powder and liberating the encapsulated fat. The process comprises contacting the milk powder with water in an amount sufficient to initiate crystallization of the lactose when subjected to heat and shearing forces and then subjecting the thus treated milk powder to shear at a temperature at or above the glass transition temperature of the lactose. The present invention is also directed to the process of making chocolate which comprise crystallizing amorphous lactose in milk powder in a process which comprises preparing a milk powder containing the crystalline lactose by the present method, then mixing the thus formed milk powder with chocolate liquor, cocoa butter and refined nutritive carbohydrate sweetener and optionally additional fat and emulsifier under conditions to form homogeneous mixture, standardizing the thus formed mixture and tempering the mixture.